Issues in Layout that do not fit into any other Layout component or which span multiple Layout components.

Bugs related to the top level presentation objects (pres shell, pres context, and document viewer), the frame constructor, and the base frame classes, as well as general issues with alignment and sizing, all belong here.

As mentioned in bug 5821, fixing this should be relatively easy: you just have to
insert an anonymous inline element around all inline content in a block, and
then set its line-height to 'inherit'. For example, the following:
<div>
<span> abc </span>
<span> def </span>
</div>
...would internally become
<div>
<anonymous-inline style="line-height: inherit">
<span> abc </span>
<span> def </span>
</anonymous-inline>
</div>
I believe that is all that is needed; David may be able to confirm or deny.
[Moving to M11 like 5821, as this should be fixed before 5821...]